Determination of dibenzopyrenes in standard reference materials (SRM) 1649a, 1650, and 2975 using ultrasonically assisted extraction and LC-GC-MS

A method has been developed for analysis of the highly potent polycyclic aromatic hydrocarbon (PAH) carcinogens dibenzo(a,l)pyrene, dibenzo(a,h)pyrene, and dibenzo(a,i)pyrene (molecular weight 302) present in small amounts in diesel and air particulate material. The method can also be used for analysis of the PAH benzo(a)pyrene, coronene, and perylene, for which reference and certified values are available for the standard reference materials used for validation of the method--SRM 1649a (urban dust) and SRM 2975 (diesel particulate matter). The only NIST values that have been published for these dibenzopyrene isomers in the analyzed SRM are reference values for dibenzo(a,i)pyrene and dibenzo(a,h)pyrene in SRM 1649a. The concentrations determined in the SRM were in good agreement with reported NIST-certified and reference values and other concentrations reported in the literature. Standard reference material 1650 (diesel particulate matter) was also analyzed. The method could not, however, be validated using this material because certification of SRM 1650 had expired. The method is based on ultrasonically assisted extraction of the particulate material, then silica SPE pre-separation and isolation, and, separation and detection by hyphenated LC-GC-MS. The method is relatively rapid and requires only approximately 1-5 mg SRM particulate material to identify and quantify the analytes. Low extraction recoveries for the analytes, in particular the dibenzopyrenes, when extracting diesel SRM 2975 and 1650 resulted, however, in the dibenzopyrenes being present in amounts near their limits of quantifications in these samples. The method's limit of quantification (LOQ), based on analyses of SRM 1649a, is in the range 10-77 pg. By use of this method more than 25 potential PAH isomers with a molecular weight of 302 could be separated.